1. Field of the Invention
The present invention relates to a continuously advancing track maintenance machine for compacting ballast supporting a railroad track comprising two rails fastened to ties, each rail including a head and having a field side and a gage side, which comprises a machine frame having a longitudinal extension substantially parallel to the track, undercarriages supporting the machine frame on the track for continuous advancement in an operating direction, a drive for propelling the machine frame for the continuous advancement thereof, a power-driven, vertically adjustable track stabilization assembly mounted on the machine frame between two of the undercarriages, the track stabilization assembly comprising rail engaging roller tools, drive means for spreading the roller tools into engagement with the gage sides of the rails, and vibrating means for imparting oscillations to the roller tools in a direction extending substantially in a horizontal plane transversely to the longitudinal machine frame extension whereby the roller tools engaging the rails transmit the oscillations to the track, and a reference system for monitoring the track level between an actual level of the track and a desired level thereof.
2. Description of the Prior Art
U S. Pat. No. 4,643,101, dated Feb. 17, 1987, discloses a continuously advancing track leveling, lining and tamping machine to which a machine frame carrying a track stabilization assembly is coupled. The machine frame may also be self-propelled and be used independently of the track leveling, lining and tamping machine. Such track maintenance machines are known as dynamic track stabilizers which considerably improve the track position solidity and particularly the resistance of the track to transverse displacement or misalignment after the track has been leveled and/or lined in a track position correction operation which includes tamping the ties of the corrected track. Since the tie tamping causes the ballast density in the cribs to be reduced, the dynamic track stabilization causes the crib ballast to be compacted so that the track immediately settles in the desired corrected position, which would otherwise be achieved only after a relatively long time by the train traffic over the track. In such a dynamic track stabilization, roller tools of the track stabilization assembly firmly grip the two track rails, and horizontal oscillations extending transversely to the track are imparted to the entire track by eccentric vibrators. At the same time, a static load is applied to the oscillating track by drives exerting a vertical force upon the track stabilization assembly so that the track is "rubbed" into the ballast which is accordingly compacted, causing the level of the track to be lowered. This operation produces not only a more permanent and uniformly elastic ballast bed but also increases the resistance of the track to transverse displacement, which is determined by the friction between the ties and ballast.
The quality of the ballast bed compaction can be derived from the value (QVW) of the resistance of the track to transverse displacement, which determines the positional stability of the track. The ballast bed quality is of particular importance for railroad tracks designed for very high-speed trains. Conventionally, this value has been measured separately from the operation of track maintenance machines. Such a measurement effected at individual ties of the track has been described in an article appearing in the periodical "Internationales Verkehrswesen", issue 1-2/81, pp. I-III (English translation in "Transport International", No. 1, Jun. 1981). In the described measurement, the rail fastening elements are first detached from the tie and the measuring device consisting of a hydraulic cylinder was attached to the tie end after ballast next to it had been removed, whereupon the tie was displaced transversely a small amount. The displacement force as well as the displacement path were measured and the QVW was derived from these measurements. After the measurement, the tie had to be moved back into its original position. This type of measurement requires considerable work and only spot measurements can be made because the ties to be tested must be sufficiently spaced apart to avoid ballast movements causing a reduction in the lateral resistance of the next tie.